MSW: derive the shut-valve trivial-equation Jacobian entry from the rate - #7314
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MSW: derive the shut-valve trivial-equation Jacobian entry from the rate#7314hnil wants to merge 1 commit into
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assembleTrivialEq, the zero-rate equation for a SHUT valve, wrote a physical rate as the residual but hard-coded its Jacobian entry as 1. The linear system solves for the scaled primary variable, so the entry has to be d(q)/d(q/s) = s; with a hard-coded 1 the Newton step for that segment comes back a factor s too small and is then multiplied by s on update. Pass the rate as an Evaluation and take the derivative from it, so the entry is correct by construction rather than by remembering to multiply. This was the only hard-coded derivative in either well assembler; every other entry already comes from an EvalWell and scales automatically. Latent until now because --well-rate-scaling defaults to 1 and every measurement so far used the default. Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
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A SHUT valve segment gets the trivial equation q = 0 in place of its pressure-drop relation, written into the segment pressure row.
assembleTrivialEqset the residual from the rate but hard-coded the Jacobian entry as1., i.e. dq/dq. That is only right while the rate primary variable is unscaled; with--well-rate-scaling=sthe primary variable is q/s and the entry must be s. Take it from the rate Evaluation instead, so it is correct by construction. This was the only hard-coded derivative in either well assembler.Effect: the linear solve returns an increment a factor s too small,
updateNewtonmultiplies by s, and the shut segment rate is multiplied by (1-s) every iteration instead of being zeroed.Reproducing needs a shut valve, which no deck in opm-tests currently has. Take
wsegvalv/BASE_MSW_WSEGVALV.DATAand set the status of one valve:then
The shut segment rate reads -3.86e-4, 1.16e-3, -3.48e-3, ... growing by (1-s) = -3 per iteration and reaching 9.96e+131 over the run; with this change it converges to zero in one iteration (max 3.9e-4 over the run). Summary output differs between the two.
Two related observations, not addressed here:
MultisegmentWellEval::getWellConvergencetests onlyisnan/isinf, with nomax_residual_allowedcomparison of the kind the mass-balance and energy branches have, so a finite 1e131 is reportedSeverity::Normalrather thanTooLarge- no timestep cut, no warning.tolerance_pressure_ms_wells(0.01 bar), so the trivial equation is never enforced tightly.🤖 Generated with Claude Code